CN1040068C

CN1040068C - Duplex adsorption process

Info

Publication number: CN1040068C
Application number: CN91108083A
Authority: CN
Inventors: F·W·莱维特
Original assignee: Union Carbide Industrial Gases Technology Corp
Current assignee: Union Carbide Industrial Gases Technology Corp
Priority date: 1990-10-25
Filing date: 1991-10-24
Publication date: 1998-10-07
Anticipated expiration: 2006-10-24
Also published as: EP0483670A1; ES2102379T3; TW201701B; CN1061161A; KR960004604B1; EP0769319A3; BR9104561A; MX9101774A; JPH07108366B2; DE69131839D1; DE69126397T2; EP0483670B1; US5085674A; EP0769319A2; DE69126397D1; JPH04265105A; EP0769319B1; DE69131839T2; KR920007671A; CA2054120A1

Abstract

A duplex adsorption process is carried out in one or more stages, each having a normal bed portion and an inverted bed portion that enables the less selectively adsorbable light component of a fluid mixture to be displaced from the normal bed portion and the more selectively adsorbable heavy component to be displaced from the inverted bed portion. Pressure swing adsorption and thermal swing adsorption processes can be employed.

Description

Dual adsorption method

The present invention relates to adopt the gas of pressure swing adsorption method (Pressure swing adsorption process) to separate, specifically relate to the rate of recovery that adopts said method to improve two kinds of product cuts that are purified.

Transformation absorption (PSA) method and system are for reaching desirable separation and purifying that wherein to contain easy selection absorbed component (more selectively adsorbable component) and be difficult for the feed stream of selection absorbed component (less selectively adsorbable componet) be well-known in the art.When feed gas under the higher adsorptive pressure on can the adsorbent bed of the said easy selection absorbed component of selective absorption through out-of-date, this easily selects absorbed component to be adsorbed.When this pressure was reduced to low adsorptive pressure level subsequently, this easily selected absorbed component desorb from adsorbent.

The PSA processing procedure is carried out in the system that comprises an above adsorbent bed usually, wherein each bed experiences certain processing procedure by endless form, comprise: (a) discharge of absorbed component---is easily selected the absorption of absorbed component---and be difficult for to be selected in charging under the higher adsorptive pressure, (b) be difficult for to select absorbed component desorb and removing under lower pressure, generally remove, and (c) should be pressurized to again under the said higher adsorptive pressure by bed from this feed end.PSA technology is particularly suitable for the air separation operation in the various industrial uses, especially for adopting the uneconomic quite small-scale operation of cryogenic air separation equipment possibility.PSA technology also very is suitable for the drying of air or other gas.

In such dry applications, humid gas is led to preferential adsorption easily select the adsorbent bed feed end of the water of absorbed component as it.Because water is adsorbed agent at this feed end and removes, so this is lost it for the adsorption capacity through wherein additional quantity humid gas by water load.Follow-up gas (being removed water) runs into quite dry adsorbent zone and discharges as the feed product of drying from this discharge end.When such drying process is proceeded, easily select the absorption forward position of absorbed component or mass-transfer zone along oppositely shifting to its exhaust end by this bed from feed end, when this absorption forward position reaches exhaust end edge or this bed almost all by water load till.Before carrying out further dry run, this bed must be regenerated, and the hydrolysis that easy selection is adsorbed is inhaled and removed from bed.When using PSA technology for drying purpose, can from bed, be removed by the water that selectivity is adsorbed, wherein make this be decompressed to lower desorption pressures from its higher adsorptive pressure, the countercurrent depressurization method that general employing makes gas emit from this feed end, and make a kind of dry flushing gas flow to its feed end from exhaust end by bed.Easily select absorption water absorption forward position thereby arrived this feed end by refoulement.In suitable designed system, when pressure when higher adsorptive pressure descends, the water impurity concentration increases in the gas, gas was emitted from this exhaust end when promptly pressure reduced in the following current depressurization steps.Be that the desorb and the required sweep gas scale of construction of water of removing easy selection absorption are less than the gas flow that is dried between adsorption cycle subsequently.Usually use a part of dry air product as purge gas, and remaining dry air is emitted from this system as final product air-flow.

Such traditional PSA technology is suitable for the purposes of this dry air, because the wet feed material air is freely to obtain, and the high-recovery of air not necessarily.That is to say that the loss of air was not the most important during waste gas flowed after purging.Yet as known to the those skilled in the art, for the purification that must be reclaimed and must not have the valuable gas of remarkable loss, this method can not be desirable or gratifying.

The typical PSA method of separating a large amount of gases is by selective absorption nitrogen and small amount of impurities (as water and carbon dioxide) and the method for producing oxygen with air.The PSA method that this separation is used is some conventional methods, except the easy selection absorbed component that is equivalent to water impurity is dense, to top similar to removing the said situation of impurity.This can cause shortening cycle-index and need suitably handle all gases during pressurization and depressurization steps.The representative example of producing the employed specific PSA process cycles of oxygen with air is disclosed among the 4th, 589, No. 888 United States Patent (USP)s of people such as the 3rd, 717, No. 974 United States Patent (USP)s of Batta and Hisock.And this method is gratifying, at least in part because feed gas (being air) be easy to obtain, and the high-recovery of product gas (being oxygen) for the economic feasibility of air separation process not necessarily.

In the application of mentioning in the above, promptly at air in the dry and application of air separation with the recovery oxygen product, to easily select absorption or be separated with the product gas that constitutes difficult selection absorbed component by more adsorbed components, promptly water separates with oxygen product gas with dry products air separation or nitrogen.This is typical conventional PSA technology.This technology generally can not be used for purify easy and select heavy component absorption or so-called.Therefore, said conventional PSA process cycles is gratifying for producing oxygen with air, but but can not be satisfactory for producing nitrogen with air.Though the gas of emitting from the feed end of bed is rich in nitrogen (comparing with air), it is too impure for most of practical applications.

In other is used, wish to reclaim and easily select component absorption or heavy as product gas, and be difficult for selecting absorption or light component remove as impurity rather than required product gas.Introduce a kind of inversion that is suitable for this purpose in the patent of Wilson (U.S.4,359,328) and pressed absorption method (Inverted pressure swing adsorption process).The method be preferably in two or many in carry out, comprising following cycle of treatment process: the absorption of (1) low pressure, (2) are pressurized to high pressure, (3) purge under said high pressure and (4) decompression discharges easily the selection adsorbed components as required product gas.In the method, feed gas (being air) is fed the low pressure adsorbent bed.Effluent air is made up of easy selection adsorbed components basically in this bed, it is forced into behind the high pressure part removes from bed as countercurrent purge gas and be difficult for the selection adsorbed components.Remaining said eluting gas is emitted as product gas (being nitrogen under the air separation situation).

The method of Wilson patent is the inverse approach of so-called conventional PSA method outwardly.But contrary PSA method is different with conventional PSA method in several importances.Reverse method after several operation cycle, heavy ends will be in the low pressure effluent enrichment and be in the product end of bed.Set up the absorption-desorption forward position in the bed, and heavy ends are in the enrichment of product end.This forward position can easily penetrate between the low pressure period of each circulation, thereby can make some light, promptly is difficult for selecting adsorbed components to enter among the product stream.Owing to this reason and other reason, reverse method needs and may or purge at high reflux ratio to carry out the heavy ends afterwards of many operation cycle under the ratio just fully by enrichment.Wilson points out, when making conventional PSA method optimization in order to improve nitrogen content in the low pressure purge effluent, does with air (80% nitrogen) that nitrogen gas concn reaches 88% under the unstrpped gas condition.For reverse method, Wison points out that nitrogen gas concn reaches 96%, and rate of recovery of nitrogen reaches 31.5%.Use for separation of air some, even this situation also may be gratifying under quite low rate of recovery of nitrogen with production nitrogen.But in other are used, the valuable gas that the reverse method of Wilson may be unsuitable for enrichment and purify and must obtain with the high product rate of recovery.

Weigh in the admixture of gas, the another kind of means of promptly easily selecting the absorbed component enrichment to use are to adopt following current displaced type PSA technology.Such PSA technology had both adopted common process, also adopted some feature of reverse technology.So, feed gas (as air) are sent into the feed end of high press and flowed to its discharge end, and the heavy ends (as nitrogen) that can easily select to adsorb are adsorbed on this bed.Light component in the air-flow (being oxygen) is discharged by this bed and as byproduct or waste gas stream.Air-oxygen forward position, the forward position that promptly is equivalent to be adsorbed in the bed nitrogen is arrived at before this discharge end, stops feed stream (being air) flowing in this.Feed end to this feeds rich nitrogen product gas then, and this makes and sets up second forward position in this bed, i.e. nitrogen-air forward position.After this moving faster than air-oxygen forward position of a forward position converged at the discharge end near this at last.At this moment, this bed is easily selected absorbed component institute's load or saturated.In case during from this feed end countercurrent depressurization, this nitrogen desorb and emit by this feed end as major product.Other nitrogen products utilize the oxygen of some recovery to make purge gas and obtain from the method for this bed of exhaust end.The nitrogen of Sheng Chaning accumulates in hold-up vessel usually like this, and the said nitrogen of some of them is compressed the back and purges air-flow as following current.Usually adopt various other treatment steps that are suitable for pressure balance and circulation to improve total handling property.The specific following current replacing process method of producing nitrogen by air be documented in Werner and Fay the 4th, 599, No. 094 and the 4th, 810, No. 265 United States Patent (USP)s of Lagree and Leavitt among.These methods can be produced nitrogen and oxygen simultaneously by air, and the rate of recovery of the two is all high, wherein nitrogen major product normally.Adopt in the practical application in industry of major diameter adsorbent bed, be difficult in and produce high-purity oxygen when producing high pure nitrogen.

Though the following current replacement cycles is for very appropriate so that the high product rate of recovery is produced nitrogen with air, it is not all gratifying that this technology runs in this area the various situations.It is found that when said heavy ends existed, this technology was ineffective especially under low concentration very.Generally speaking, when the desorb of easy selection absorbed component under the vacuum or the pressure more much lower than adsorptive pressure (this pressure separate for many gases or purify may be inapplicable or uneconomical) under when carrying out, this following current replacing process process can be carried out satisfactorily.

In the moving bed process method of being shown the simulation of mentioning in＜absorption principle and adsorption process〉book (Wiley andSons,, the 396th～405 page in 1984) by D.M.Ruthven is the representative of other known PSA process.This method can be produced some high-purity gas with the high product rate of recovery under certain conditions, but but very complicated and cost is high, needs to adopt many adsorbent beds and valve usually.In addition, when the adsorption isotherm aggressive bend of heavy ends or exist severally when having the strong absorbed component of different balance isotherms, this technical process is usually finished badly.

Introduced another kind of PSA process in the 4th, 354, No. 859 United States Patent (USP)s of Keller and Kuo, this method is separated into two kinds of product air-flows by carry out the periodic pressure variation at the adsorbent bed two ends with feed gas.The method and system (are called as the molecule gate: molecular gate) utilize some pistons to produce periodically gas flow and pressure variation at the bed two ends, simultaneously charging is imported at middle certain point.Regulate the swept volume of this opposed pistons effect and productivity ratio and the selectivity that phase angle is controlled this technology.Though this technology and system can make two kinds of product air-flow outputs, but be difficult to expand to commercial scale and operation economically.As a result, this molecule gate method is not used on industrial gasses separation or the purification operations as yet.

Therefore, still need a kind of improved PSA process in this area at present, this method is simple, only uses a few adsorbent bed, and can be used for purifying or the separating feed air-flow under the high-recovery of required one or more product gas.

One of the object of the invention provides a kind of improved PSA process, and it is two kinds of purifying gas flows that this method is used to separate the multicomponent feed stream, and required purified product gas does not have significantly sacrificing.

The improved PSA process that it is two kinds of pure air-flows that two of the object of the invention provides a kind of effective separation bi-component air-flow, and the rate of recovery of two components is all very high in the said air-flow.

The 3rd purpose of the present invention is to provide a kind of PSA process, and this method is suitable for producing the air-flow that purifies from being difficult for selecting to remove the adsorbed gas impurity of easy selection absorption under the high-recovery of required product gas.

Another purpose of the present invention is to provide a kind of PSA process, and this method is suitable for removing the impurity that is difficult for selecting absorption from easy selection adsorbed gas, produces the air-flow that purifies under the high-recovery of required product gas.

Another object of the present invention is to provide a kind of improved PSA process, this method is suitable for removing trace nitrogen from impure argon, so that the argon gas product losses is only for producing the straight argon air-flow under the condition of ignoring in purification process.

In view of these purposes and other purpose, hereinafter describe the present invention in detail, its new technical feature specifically indicates in appended claim.

Each adsorbent bed is divided into two sections, feed points is set so that a kind of complete dual PSA process and system to be provided therebetween.First section PSA technological operation routinely, second section with reverse PSA technology mode operation.In the whole technology each step from one section to two sections of another sections all with level and smooth stream operated.Be sent to reverse section low pressure feed end from the low pressure eluting gas of conventional section, and be sent to the feed end of conventional section from reverse section high pressure eluting gas.Gaseous mixture or impure gas incoming flow are all injected from being in conventional section and reverse intersegmental feed points in high pressure and/or periods of low pressure.Implement when of the present invention, this PSA process and system can work as complete binary piece-rate system, and produce highly purified light component and/or heavy ends under its high-recovery.

Below present invention will be described in detail with reference to the accompanying, wherein:

Fig. 1 is the schematic diagram that used two two PSA systems when enforcement is of the present invention are described.

Fig. 2 is the schematic diagram that used four two PSA systems when enforcement is of the present invention are described.

The present invention seeks to by providing a kind of PSA process that the technical characterictic of conventional and reverse PSA method is combined to reach.Two transformation processes of integral body of the present invention and system can produce pure and concentrated product air-flow, and do not have own the intrinsic the sort of product loss that occurs of not wishing in routine or the reverse PSA technological operation.The present invention is particularly suitable for and must removes light component or heavy ends impurity from valuable gas under very little or negligible loss (being under the high-recovery), reclaims product gas.

Those skilled in the art know, conventional PSA technology is generally carried out in two or many, wherein each bed all experiences a kind of pressurization-decompression process periodically, easily selects absorbed component or heavy ends to be adsorbed under higher adsorptive pressure in this process, and than desorb under the low desorption pressure.Each bed is delivered to the feed end of bed after feed gas is compressed under the higher adsorptive pressure in this conventional treatment operation, heavy ends are by preferential adsorption, and at least some light components are removed from its discharge end as the light gas product that purifies.The remaining gas of emitting from this discharge end in the high pressure adsorption step is used to provide a kind of countercurrent purge gas of low pressure and is sent in this system another discharge end after easy expansion.When first adsorption capacity (reaches as indicated in its discharge end edge by bed as the absorption forward position of easy selection absorbed component) when exhausting like that, termination enters this feed stream, and begins the decompression phase of this circulation.At this moment, first general using reduced pressure by following current from the method for this discharge end emission gases.The discharge end that the gas of so emitting from this discharge end is preferential to enter second or this system another after expanding makes pressure balance and/or purge gas is provided.Then, emit gas along with countercurrent depressurization with from this feed end, this is further depressurized under the lower desorption pressures, contain the easy selection absorbed component in the feeding gas in the gas of being emitted and it delivered in the waste gas, perhaps when to be difficult for selecting adsorbed components be required product gas used as other purposes.To be in send into sweep gas than this discharge end under the low desorption pressure after, this bed is forced under the higher adsorptive pressure once more.Generally speaking, will feed said first discharge end from the gas that another discharge end of second or the experience decompression of this system is discharged and carry out pressure balance, and can make this bed from being pressurized under the middle pressure once more than beginning under the low desorption pressure.Then, make feed gas feed this feed end, its pressure is brought up under the high adsorptive pressure from middle pressure.Then, continue under this high adsorptive pressure, to make feed gas to feed this feed end, be difficult for that adsorbed components continues in said first along with this periodical operation and therefrom discharge.

For operation effectively, must make the heavy ends that all are adsorbed basically remove and drain into the waste gas from this feed end.For desorb with purge easy selection absorbed component in this, a certain minimum flow light component will inevitably be lost in the waste gas, and loss amount depends on the sorbent material that uses in the component that related to, the bed and relevant pressure ratio or the like.The rate of recovery of lighter-than-air gas component is limited by these mainly, especially is subjected to peculiar high absorption in this PSA technology to press restriction with the ratio of low desorb pressure.Therefore, in the separation that is difficult for the selection absorbed component was reclaimed, this conventional PSA method was limited in relating in the application of the low valuable feed stream of separation selectivity.

Above-mentioned conventional PSA technology can be undertaken by various variation schemes.Therefore, can adopt vacuum and super-atmospheric pressure, also can adopt multibed system, wherein carry out circulating treatment procedure periodically in each bed, and each other bed also carries out said processing procedure in the system, so that implement the pressure conversion step under the condition of not interrupting whole system feed stream and product stream.The many different processing procedure that is used to improve concrete separating technology performance is disclosed in the prior art, for example about the processing procedure of various decompressions, pressure balance and purging aspect.These variation schemes are subjected to same inherent limitations aspect the light difficult selection absorbed component all reclaiming.

When implementing reverse PSA technology, feeding gas is delivered to system under low pressure (as atmospheric pressure) first.In this step, be difficult in the feeding gas selecting the light component of absorption to be adsorbed, because its component pressure (or dividing potential drop) is higher than when initial and the entire process process in the pressure of this component in this after each depressurization steps, and said entire process process comprises: the absorption of (1) low pressure, emit easy selection adsorbed components simultaneously, (2) pressurization, (3) remove enrichment waste gas under the high pressure, promptly be difficult for selecting adsorbed components, and (4) decompression, the heavy ends of under low pressure emitting easy selection absorption simultaneously are as the required highly purified product that has.Difficult selection adsorbed components in the admixture of gas thereby replacement with exhaust adsorbent on the gas component of easy selection absorption in being adsorbed mutually.As a result, easily selecting the advancing vapor phase areas of absorbed component to be in contains before the gas phase zone of easy and difficult selection absorbed component simultaneously.

The increase of pressure causes the selective absorption of easy selection absorbed component in the middle bed of reverse method step (2).This phenomenon causes exhausting the easy selection absorbed component in the gas phase, and causes being difficult for selecting absorbed component corresponding enrichment in gas phase.In step (3), purge adsorbent bed, be used for from this adsorbent bed, removing the gas phase that is rich in difficult selection absorbed component with easy adsorbed components.The decompression of this adsorbent bed thereby cause easy selection absorbed component under the purity that improves, from this bed, to emit.When implementing reverse PSA method, can also adopt other technology characteristics when needing, for example pressure equalization step etc.But even said technology characteristics and constrained optimization, the heavy ends of significant quantity also can be present in the step (3) among the waste gas stream of removing under the high pressure.Therefore, reverse PSA technology and system only are suitable for processed feed stream and are worth and concentrate when low or the actual process operation of enrichment heavy ends product.

Fig. 1 describes of the present invention pair of PSA technology and system in detail, and wherein unstripped gas is sent in each bed of two bed systems from its intermediate point.In contrast, but unstripped gas is delivered to the feed end of each in the above in the conventional PSA that mentions and reverse PSA technology and the system.In the scheme of Fig. 1, unstripped gas in the pipeline 1 with compressor 2 compressions after, perhaps pass through valve 3 after, the intermediate point 5 between bed 4 two ends is sent in the adsorbent bed 4, perhaps is sent in the bed 7 from its intermediate point place through valve 6 backs.The light component of removing from bed 4 upper ends is sent to the pipeline 10 through valve 9 and reclaims as light product gas.The light component of being removed by bed 7 upper ends also is sent in the said pipeline 10 as said light product gas recovery through valve 11 in a similar manner.The light component of removing from the top of each can be sent to another top through the pipeline 12 that comprises valve 13.

By the heavy ends that remove bed 4 bottoms, can send in the pipeline 16 that comprises valve 17 via the pipeline 14 that comprises valve 15 and reclaim as the heavy ends product gas.Can deliver in the said all-product line 16 via the pipeline 18 that valve 19 is arranged in a similar manner by the heavy ends that discharge bed 7 bottoms.The heavy ends of being discharged by

bed

4 and 7 also can be sent into compressor 22 through

valve

20 and 21 respectively and before reclaiming as the heavy ends product or among the selectivity hold-up vessel 23 before being recycled in this system.Valve 24 and 25 are set, and purpose is to make this system to remain in operation easily under loading condition not and need not the unnecessary compression of unstripped gas and heavy ends product air-flow.

System shown in Fig. 2, except each becomes four bed systems at said feed points punishment open form, substantially the same with two two transformation systems among Fig. 1.Therefore, the scheme of Fig. 2 is come with the bed that separates separately 4 and 4a and 7 and 7a, and unstripped gas is from being among the

pipeline

5 and 8 that every pair of bed intermediate point place sends into separately with every pair of bed communicates.

Should be known in and implement when of the present invention, the top of two transformation systems, promptly the top of

bed

4 and 7 in the top of bed 4 and Fig. 2 scheme in Fig. 1 scheme plays the sort of effect of light product end of system in the conventional PSA technology.Similarly, the bottom of two transformation systems, promptly the bottom of

bed

4a and 7a in bed 4 bottom and Fig. 2 scheme in Fig. 1 scheme plays the sort of effect of heavy ends product end in the reverse PSA technology of Wilson.

Embodiment for detailed description with reference to Fig. 2 is described, and will contain the binary mixture of light and heavy ends, promptly is difficult for delivering to compressor 2 with the unstrpped gas of easily selecting the mixture of absorbed component in pipeline 1 and is compressed under the high adsorptive pressure.In time, compressed unstripped gas is delivered in the pipeline 5 so that it is fed the bottom of bed 4 in the section processes of entire process circulation through valve 3.Pass bed 4 after this unstripped gas converges with effluent from bed 4a upper end and upwards flow, wherein heavy ends are adsorbed, and the light component of remaining difficult selection absorption passes this bed and flows out from bed 4.A part is emitted as light product in pipeline 10 through valve 9 through the light gas stream of purifying like this.After expanding under the low-pressure through valve 13, all the other lighter-than-air gas through purifying enter the light product end in top of bed 7.This low-pressure gas backflows by bed 7, and the process of backflowing mesolow gas displaces the heavy ends that are adsorbed in advance the previous step of said cyclic process from this.The effluent of so emitting via its bottom from bed 7 is directly delivered to the top of a 7a by pipeline 8, and heavy ends are driven away in its continuation effect in bed 7a from bed 7a bottom.Effluent from bed 7a is compressed and sends into hold-up vessel 23 through valve 21 backs in compressor 22.Part inventory of gas in 23 is emitted as heavy product via pipeline 16 and valve 17 and is reclaimed, and from this gas of another part of hold-up vessel 23, process pipeline 14 and valve 15 are sent to the bottom of a 4a.This gas is flowed forward pass a 4a and displacement light component wherein.After merging with the unstripped gas that is passed into pipeline 5 via pipeline 1 and valve 3 from the effluent of bed 4a (ideally its composition can near flow of feed gas), enter the lower end of bed 4.This step in the whole circulation processing procedure must penetrate bed 4 in the absorption forward position of easily selecting absorbed component and feed by this system or this system of part and emit and stopped to the light product gas of bed 7 upper ends recirculation via pipeline 12 and valve 13.

In time,

bed

4 and 4a reduce pressures from high adsorptive pressure at the next step of this PSA processing procedure, and

beds

7 and 7a increased to again under the said high adsorptive pressure from low desorption pressure.In a kind of desirable scheme, recover in order to obtain required pressure, adopted pressure equalization step.For this reason, between bed, reach and to end in pressure balanced that time to this system feeding with from this system's discharging.For this reason, with

valve

3,9,11,15,19,20 and 21 Close Alls, valve 13 is still opened, up to owing to enter and be initially located in low desorption pressure 7 tops of leaving the bed from being initially located in gas that bed 4 tops that high absorption depresses emit, when making pressure balance arrive to a certain degree till.Shut off valve 13 then,

open valve

19 and 20, so that

bed

4 and 4a can be further depressurized because of emitting gas from bed 4a bottom,

bed

7 and 7a flow into bed 7a bottom owing to the gas from hold-up vessel 23 and further be pressurized under the high adsorptive pressure again simultaneously.During these steps are carried out, when need not be, can open

valve

24 and 25, so that make these units continue operation under the loading condition from the air-flow of

compressor

2 and 22.

In the follow-up time of this processing procedure, upwards flow through high adsorptive pressure bed 7 through pipeline 8 and valve 6 from the unstrpped gas of compressor 2.The light product of some purifications that separate with the heavy ends of easy selection absorption in the bed 7 reclaims with the light product form through valve 11.Remainder is sent into the upper end of bed 4 after the light product of purification expands by valve 13, be passed down through this therein and replace the heavy product of absorption in the past.Be passed down through pipeline 5 from the effluent of bed 4 and enter a 4a upper end, flow downward therein, carry the additional quantity heavy ends gas of absorption in the past simultaneously.The effluent of bed 4a is compressed in compressor 22, and enters among the hold-up vessel 23 through behind the valve 20.Portion gas in the hold-up vessel 23, by the road 16 and valve 17 emit as heavy product gas, and the remaining gas in the said hold-up vessel 23 is passed pipeline 18 and valve 19 backs feed bed 7a as substitution gas bottoms.After the effluent of bed 7a and unstripped gas merge, be admitted to the bottom of bed 7 in pipeline 8.This adsorption wave that operates in a 7a and 7 stops before penetrating the effluent of being emitted by said bed upper end.

In the final step of said entire process process, carry out pressure balance operation by second step of total processing procedure, so that recover to be initially located under the high adsorptive pressure all pressure and make all of being initially located in low desorption pressure under be pressurized to higher intermediate pressure.During the termination pressure balancing run, shut off valve 13 is opened

valve

15 and 21, make the

bed

7 and 7a further reduce pressure and make the

bed

4 and 4a pressurizeed again.In case so finish said processing procedure, then use and send into other unstrpped gas in this and to repeat said cycling by the sort of processing procedure of top general introduction.

Therefore enforcement of the present invention as can be seen can make and be difficult for selecting the light component of absorption to be substituted and to obtain to reclaim at an end of said system, and easily selects the heavy ends of absorption to be substituted and to reclaim at the other end of said system.This pair of pressure swing adsorption method adopts a kind of like this system, this system has a transformation adsorption stage that contains sorbent material at least, and said sorbent material can be from the heavy ends that contains easy selection absorption and is difficult for selecting absorption the raw mix of light component of absorption easily to select the heavy ends of absorption.In various solid yardage cases, according to summer condition relevant and preferred two-stage or the multilevel system of adopting of requirement with concrete purposes.When selecting to adsorb like this, the absorption forward position of the reorganization branch of said easy selection absorption is easy to form in said adsorption stage.Every grade all has conventional bed part above-mentioned and reverse part, and every grade all experienced above-mentioned processing procedure periodically, and its generality is summarized as follows:

Under high adsorptive pressure, the bottom with reverse part in the said level of heavy ends feeding of easily selection absorption therefrom displaces the light component that is difficult for selection absorption.From the gaseous effluent that the quilt on the said reverse bed part so displaces, under high adsorptive pressure, be sent to the lower end of conventional bed part in this grade, make it to advance and therefrom pass through.Be difficult for the upper end discharge of light component conventional bed part in this grade of selection absorption.Make this level be decompressed to low desorption pressure then from high adsorptive pressure.

Then, the difficult light component of selecting to adsorb is fed conventional bed upper end partly under low desorption pressure, make it oppositely therefrom to pass through, so that the therefrom displacement heavy ends of absorption in the past.By the gaseous effluent that conventional bed bottom displaces like this, under low desorption pressure, feed the upper end of reverse bed part, so that under said low desorption pressure, therefrom displace the additional quantity heavy ends.Easily select the heavy ends of absorption under said low desorption pressure, to discharge from the bottom of reverse bed part.Then, with this level from the paramount adsorptive pressure of low desorption pressure supercharging.

Should know, material gas mixture to be separated, in following all steps during at least one step, can be among the conventional bed part of this grade and the place, centre position between the reverse bed part be admitted to this level: (a) heavy ends are fed the reverse bed of this grade bottom partly, (b) this level presses decompression power to low desorption pressure from high absorption, (c) light component is sent into the conventional bed of this grade upper end partly, and (d) made this level from the paramount adsorptive pressure of low desorption pressure supercharging.In case finished this processing process, just use the other material gas mixture, according to and whole system in the required relation that experiences equally between other grade of said processing procedure repeat said all treatment steps.

For some embodiments, should preferably under high adsorptive pressure, during the heavy ends of said easy selection absorption feed the bottom of reverse bed part in this grade, raw gas mixture be entered in this level.But, in the other embodiment, requirement according to known application, at the light component that will be difficult for selecting adsorbing during this step of upper end that feeds conventional bed part under the low desorption pressure, perhaps during pressurization or depressurization steps, perhaps the Assemble Duration of said all steps adding raw gas mixture may be preferred.

Though with reference to every grade the conventional bed part and the following or bottom and the upper end of reverse bed part the present invention has been described herein, should have known that said only is for the ease of consistent with all parts position of bed shown in the accompanying drawing with reference to top and bottom.Yet, in practical application in industry, all levels, its various piece and outflow and inflow between said level or part are set according to required alternate manner, also belong to the scope of the invention.

Though the two pressure swing adsorption methods of top reference have illustrated the present invention, adopt dual absorption method to come separation fluid mixtures also to belong to the scope of the invention in alternating temperature (themalswing) process program.In this alternating temperature absorption (TSA) operation, low adsorption temp is equivalent to higher adsorptive pressure, and higher desorption temperature is equivalent to than low desorption pressure.Should be known in that the PSA technological operation comprises pressurization and the measures to reduce stresses to all levels and supply feed stream wherein, and the TSA technological operation comprises all levels and supply feed stream wherein heats or the corresponding measure of cooling.For this heating operation, can adopt indirect or with the tube bank heating that is embedded in Zhu Jizhong.Heat exchanger can be used for required cooling, and absorption and desorb water that compression and air exhausting device can be conveniently used for reaching required in the PSA operation are flat.

As shown in figs. 1 and 2, each PSA or TSA level all can comprise the single bed of a sorbing material, perhaps every grade all can comprise several independently adsorbent bed as conventional bed part and reverse part of each grade.General preferred at least two PSA levels or TSA level, but in the separation of the particular fluid with special process requirement, single level system may be that plan is required.

Implement when of the present invention, the light component of the difficult selection absorption of discharging by the upper end of certain grade of conventional bed part, a part reclaims in this system usually, as required product or byproduct, is perhaps discharged by this system as the waste stream of fluid lock out operation; The said light component of another part is passed into one or multistage upper end usually during displacement step, wherein for the PSA method, under low desorption pressure and for the TSA method, under high desorption temperature, this light component fed certain grade in the upper end of conventional bed part.Similarly, the heavy ends of the easy selection absorption of discharging by the lower end of reverse bed part in certain grade, a part reclaims as required product or byproduct usually, perhaps discharges from system as the waste stream of fluid lock out operation; After the said heavy ends of another part are compressed or cool off, send into one or multistage lower end in displacement step, said heavy ends are sent to the lower end of its reverse bed part under high adsorptive pressure (for the PSA method) or low adsorption temp (for the TSA method) in this step.Be to be understood that the said light and heavy ends of this part of discharging from one-level can be as in other all level or discharge displacement fluid in this part the level, this decides on the relevant situation of implementing to be adopted when of the present invention of whole system.

In system with two or more PSA or TSA level, pressurization of this method and decompression, perhaps heating and cooling step, preferably include some equilibrium steps, in equilibrium step, make gas flow into the one-level that is initially located in low pressure or low temperature, so that by recovering energy like that of pointing out below from the one-level that begins to be under high pressure or the high temperature.

The inventive method can be used for finishing various industrial valuable fluids and separates.PSA embodiment of the present invention is used for gas and separates, and is very desirable as argon gas-oxygen separation and purification for argon operation.Separate at typical argon-oxygen and to use, the air-flow that contains 96% oxygen and 4% argon approximately can be used for producing that to contain oxygen be 98% or higher, the high purity oxygen air-flow as 99.5%.Also can obtain the air-flow of rich argon, as the air-flow of 50% argon-50% oxygen or more high purity argon stream, for example air-flow of 95% argon.In these operations, argon gas is the light component that is difficult for selecting absorption, and oxygen is the heavy ends of easily selecting absorption.In purification for argon operation, argon gas is separated in hydro carbons, carbon monoxide, carbon dioxide and the ammonia as light component for example oxygen or nitrogen from heavy impurity.In other purification for argon operation, heavy argon product is separated from light impurity such as hydrogen, helium or neon.Helium or hydrogen cleaning are other ideal application of the present invention, and wherein light helium or hydrogen production for example reclaim nitrogen and the methane from heavy impurity.In other desirable PSA separated, the present invention can be used for separation of methane from natural gas; From methane and carbon dioxide, isolate nitrogen; From carbon monoxide, isolate nitrogen; Remove heavy seeds and purify xenon and krypton; From heavy seeds, reclaim nitrogen and methane etc.

TSA technology with industrial significance comprises that gas separates, and for example separates from heavy carbon monoxide and/or carbon dioxide component and reclaims light nitrogen; And fluid separation applications, for example from as separating the ethanol of light component and reclaiming as the water of heavy ends and from the mixture of positive structure hydrocarbon and isohydrocarbon, separate and reclaim positive structure hydro carbons.

Those of ordinary skills know, can make various changes and modifications on all invention details as herein described and can not exceed the invention scope that defines in the claims.For example, can be from the heavy ends that contain easy selection absorption and be difficult for selecting the sorbing material of the said heavy ends of selective absorption the unstripped gas of light component of absorption or other fluid mixture, can be used for implementing the present invention.The balanced type sorbing material, for example zeolite molecular sieve (as traditional 13X and 5A) as speed type selective absorbent (rate-selective adsorbent materials) (as acticarbon and 4A molecular sieve), can use.People also know, used progression can change, and can change said treatment process according to practice known in PSA and the TSA field, and especially in transformation or alternating temperature step, make change, whole operation is carried out reposefully and therefrom successfully flow out required product.

The present invention's dual PSA technology is specially adapted to remove heavy impurity from valuable and the light component that is difficult for being adsorbed.In this case, require lighter-than-air gas that the high rate of recovery is arranged, thereby can not obtain with traditional PSA technology.Its instantiation is to remove nitrogen from the impure argon stream that contains 100ppm nitrogen approximately.Need the super-atmospheric pressure operation to enter argon gas to guarantee that surrounding air can not be leaked.Use system shown in Figure 1, the impure argon feed stream of employing when 210kPa and desorb are pressed to 105kPa, thereby the pressure ratio that provides in this case is 2: 1, do not require vacuum.When environment temperature is 300 ° of K, under 210kPa, be in the 13X molecular screen material adsorbent bed of poised state in the argon with 100ppm nitrogen, under 105kPa, be in poised state with the described nitrogen of 172ppm.The nitrogen of removing easy selection absorption by low pressure displacement step of the present invention need be used for this low pressure displacement step with at least 58% adsorbent bed discharge air-flow.In practice, 60% or more displacement stream be used for compensating any nonideality of this technology in this case, and guarantee the purity that reaches desired.Iff using common process to be low to moderate 60% displacement stream, then the rate of recovery of argon gas will be limited to approximately 40%, and this is unacceptable in industrial practice.This rate of recovery can only promote high pressure or adopt the vacuum desorption means to increase by improving pressure ratio.Yet the rate of recovery of this traditional handicraft remains poor, and this technology is unsafty to this purification for argon and reclaimer operation.

In the dual technology of the present invention, routine effluent is partly circulated into reverse bed part.About this special applications, this part is with high reflux ratio, and the ratio of high pressure displacement air-flow that promptly flows forward and the low-pressure air current that flows is backward operated.

Be close to pure argon gas for initial filling in the bed, nitrogen gas concn slowly increases in the hold-up tank, and reaches a limit that depends on valve 17 discharge rates in described Fig. 1 embodiment.If only 1% light product flows discharge valve 17, then the composition of hold-up tank finally reaches and contain 1% nitrogen in argon gas.This rate of recovery corresponding to argon gas is about 99%.For higher emission index, then concentration is low more, and the rate of recovery is just low more, otherwise for lower emission index, the concentration of nitrogen is high more, and the rate of recovery of argon gas is just high more.People know clearly that the economic limit of the argon gas rate of recovery decides the economic evaluation by relevant any given application, but can obtain to surpass 99% the rate of recovery when implementing the present invention's duplex skill.It is an example that feed stream is separated into the light and heavies stream that purified that air separation is become oxygen (adding argon gas) and nitrogen.In many this application, only need single product, oxygen or nitrogen, and other component is used as the refuse discharge.In these cases, the high product rate of recovery may be little important, because ambient air is the nature thing, so in this case, does not need dual technology of the present invention.Wishing that refuse is minimum if two kinds of products all are valuable, is favourable and use this dual technology.

And, when feeding air be compressed with preliminary treatment when removing water vapour or carbon dioxide, for example, it no longer is so-called natural goods, then from the economic point of view, high-recovery is important.Dual absorbing process of the present invention can obtain the desired rate of recovery.

When making this air separation according to Fig. 2 embodiment enforcement the present invention, gas under high pressure flows forward in

bed

4 and 4a, under low pressure flows backward in bed 7 and 7a.Nitrogen is discharged by desorb from

bed

7 and 7a, is adsorbed under high partial pressures in bed 4a then again.People know clearly, in this air separation was used, absorption the mobile of forward position was in check, thus heavy product be nitrogen to contain few light component, promptly high-purity form of oxygen and argon gas obtains.Therefore, can allow seldom penetrating or not penetrating of desorb in the reverse bed part or absorption forward position.For each part of certain grade, this forward position moves forward as the absorption forward position during the step of high pressure that gas flows forward.Move backward as the desorb forward position in this forward position during the low pressure steps that gas flows backward.In conventional bed part, desirable forward position move be during all flow steps forward of this application to not far the moving backward during all flow steps backward of reach.This can be guaranteed by the substitution gas backward that use is a sufficient quantity with respect to clean product stream forward.

In reverse bed part, move in desirable forward position be that moving backward during all flow steps backward is not distal to moving forward during all flow steps forward.This substitution gas forward that can not be sufficient quantity by use with respect to clean product stream backward simply is guaranteed, because forward position speed is under high pressure lower than under low pressure with the ratio of gas flow rate.Even the gas that leaves reverse bed part end all as forward substitution gas, does not stay as the product of miscarrying after clean at all, this forward position also can be moved further during flow step after the constant voltage.Penetrate for fear of using relevant occurring in this case, can implement the transformation step and the forward position be moved forward be distal to backward and move with said air separation.And during the transformation step, do not use a large amount of clean gases of stream forward just can realize this point, because any such pure qi (oxygen) stream all needs flowing backward only of balance during all constant voltage steps, this often makes this situation degenerate easily.

As a result, during pressurization steps, use before the omnidirectional air-flow and after using omnidirectional during the depressurization steps air-flow implement the present invention and carry out said air separation.In a step, the pure rich heavy ends gas of stream before the bottom of reverse bed part feeds makes whole level (comprising conventional bed part and reverse bed part) pressurization with this method.In corresponding depressurization steps, feed the pure rich heavy ends gas that backflows by reverse bed lower end partly.This two steps average pressure is almost equal, so the ratio of average speed is also almost equal between absorption forward position speed and local air flow speed.The total air flow of this reverse bed part lower end is also almost equal.But the mean place in this forward position and is compared during the depressurization steps, and more near the reverse end of this grade, local gas is mobile strongly in addition, and strong more the closer to reverse end during pressurization steps.This variation of local air flow speed provides required difference on the speed of absorption forward position.The result be during all transformation steps this forward position move forward very greatly only, be enough to offset the sort of during all constant voltage steps and move backward only.So, when said cycling was carried out, total clean moving can be ignored and go to zero.

People know, need adopt some suitable transformation steps to come balance fast moving and prevent that unwanted light component from penetrating and entering in the heavy ends product forward when air separation.As the purification for argon purposes of mentioning, generally can adopt mass air flow in the above at the conventional bed part end of this grade.But in this operation that this air separation is used, the moving of forward position in the reverse part of this grade can not be with the backflow balance of any amount, and in a large number and be that the light component of not permissible dose can escape among the heavy ends product.

When implementing this dual absorbing process operation for air separation, preferably close the method for other valve simultaneously and carry out the pressure balance operation of all heavy ends product end with for example opening valve 26 in the pipeline 27.This step proceed to pressure among a 4a and the 7a almost equal till.Pressure in the

bed

4 and 7 can still preferably make whole balances cross valve 26 with air communication and reach this purpose by the method while balance of the valve 13 of flowing through.After the pressure balance, shut off valve 26 and 13 (if being in opening) is opened

valve

20 and 19, and compressor 22 is worked on, so that reduce pressure and the pressure that improves among bed part 7 and the 7a among bed part 4 and the 4a.

Usually implement when of the present invention and superincumbent illustrative example in, all the other steps of said cyclic process by to said air separation purposes in similar mode carry out, be all valves should switch effectively

bed

4 and 7 and

bed

4a and 7a in the position.

When the attached technology of this double suction is carried out the air separation operation under 300 ° of K, high pressure is 105kPa, low pressure is 70kPa, use the 13X adsorbent of molecular sieve, total bed volume is 360 meter 3, i.e. 252000kg adsorbent, and circulation timei is 60 seconds, oxygen and the argon gas light component product of the about 10ppm of nitrogen gas concn can be under the accurate overall recovery of 99.9+%, obtained under these conditions, and the nitrogen heavy ends product of oxygen and the about 5ppm of argon content can be under the accurate overall recovery of 99.9+%, obtained.

The attached technology of double suction of the present invention will provide a kind of progress that very needs in adsorbing domain.Because the light component of the difficult selection absorption in the material flow mixture and the heavy ends of easily selection absorption all can be reclaimed under the high-purity and the rate of recovery, so the present invention can make desired adsorption technology, no matter be transformation absorption or alternating temperature absorption, be effectively applied among the practical application in industry that industrial value increases day by day.

Claims

1. be used for two pressure swing adsorption technique methods at the system's separate raw materials admixture of gas that has a transformation adsorption stage at least, contain sorbing material in the said transformation adsorption stage, said sorbing material can adsorb the heavy ends that said easy selection is adsorbed from the said raw gas mixture that contains easy selection heavy ends of adsorbing and the light component that is difficult for selection absorption, form the absorption forward position of the heavy ends of said easy selection absorption thus in said adsorption stage, said adsorption stage has conventional bed part and reverse bed part and experiences the processing procedure that comprises the following step periodically:

(a) under high adsorptive pressure, make the heavy ends of said easy selection absorption feed reverse bed bottom partly in the said level, from wherein replacing the light component that is difficult for selecting absorption, the gaseous effluent that so displaces from said reverse bed upper end partly is passed into the lower end of conventional bed part the said level under said high adsorptive pressure, make it mobile forward;

(b) light component that is difficult for selecting absorption is discharged in the upper end of conventional bed part from said level;

(c) make said level be decompressed to low desorption pressure from said high adsorptive pressure;

(d) under said low desorption pressure, the light-component gas that is difficult for selection absorption is fed conventional bed upper end partly, make it along the reverse flow mistake, so that therefrom displace the heavy ends of prior absorption, the gaseous effluent that displaces from conventional bed bottom partly is admitted to the upper end of said reverse bed part under said low desorption pressure like this, therefrom to displace the additional quantity heavy ends under said low desorption pressure;

(e) bottom from said reverse bed part emits heavy ends under said low desorption pressure;

(f) said level is pressurized to high adsorptive pressure from said low desorption pressure;

(g) in said step (a), (c), (d) and (f) during at least one step in, the intermediate point between said conventional bed part and reverse bed part feeds said raw gas mixture to said level; And

(h) with the said raw gas mixture of additional quantity, repeat said step (a)-(g) periodically, be difficult for selecting the light component of absorption and easily select the heavy ends of absorption all under high-recovery, to be reclaimed with high-purity thereby make.

2. the process of claim 1 wherein and raw gas mixture is being fed in the said level at said intermediate point during the said step (a).

3. the process of claim 1 wherein and raw gas mixture is being fed in the said level from said intermediate point during the said step (d).

4. the process of claim 1 wherein that every grade includes single adsorbent bed.

5. the process of claim 1 wherein that every grade includes the adsorbent bed that separates that is used for conventional bed part and is used for reverse bed part.

6. the process of claim 1 wherein that said system comprises two transformation adsorption stage.

7. the method for claim 1, wherein a part reclaims from said system from the light component of the difficult selection absorption of step (b) discharge, another part is used for therein delivering to during (d) step one or multistage upper end, and the heavy ends that the easy selection that a part is discharged in step (e) is adsorbed are reclaimed in said system, and another part is used for therein sending into during the step (a) one or multistage bottom.

8. the method for claim 1, wherein said system comprises two or a plurality of transformation adsorption stage, and depressurization steps (c) and pressurization steps (f) comprise gas is fed another grade that is initially located under the low pressure and comes balance pressure therebetween from being initially located in one-level under the high pressure.

9. the process of claim 1 wherein that said raw gas mixture comprises as the oxygen of the heavy ends of easily selecting absorption with as the mixture of the argon gas of the light component that is difficult for selecting absorption.

10. the process of claim 1 wherein that said raw gas mixture comprises as the argon gas of light component that be difficult for to select absorption with as the impurity of easily selecting the heavy ends of absorption.

11. the process of claim 1 wherein that said raw gas mixture comprises as the helium of light component that be difficult for to select absorption with as nitrogen and the methane of easily selecting the heavy ends of absorption.

12. the process of claim 1 wherein that said raw gas mixture comprises as the hydrogen of light component that be difficult for to select absorption and as the impurity of easily selecting the heavy ends of absorption.

13. the process of claim 1 wherein that said raw gas mixture comprises as the xenon of light component that be difficult for to select absorption with as the impurity of easily selecting the heavy ends of absorption.

14. the process of claim 1 wherein that said raw gas mixture comprises as the krypton of light component that be difficult for to select absorption with as the impurity of easily selecting the heavy ends of absorption.

15. be used for two temperature swing adsorption process methods in the system's separation fluid mixtures that has an alternating temperature adsorption stage that contains sorbing material at least, said sorbing material can adsorb said heavy ends from the raw gas mixture that contains easy selection heavy ends of adsorbing and the light component that is difficult for selection absorption, in said adsorbent, form the absorption forward position of the heavy ends of said easy selection absorption thus, every grade all has conventional bed part and reverse bed part, and experiences the processing procedure that comprises the following step periodically:

(a) under low adsorption temp, the heavy ends of said easy selection absorption are sent into the bottom of reverse bed part in the said level, from wherein replacing the light component that is difficult for selecting absorption, the fluid effluent that displaces from said reverse bed upper end partly is sent to the lower end of conventional bed part the said level under said low adsorption temp like this, makes it to pass through forward;

(c) said level is heated to high desorption temperature from low adsorption temp;

(d) under said high desorption temperature, the light component that is difficult for selection absorption is fed conventional bed upper end partly, make it the reverse flow mistake, thereby therefrom displace the heavy ends of prior absorption, the effluent that so displaces from conventional bed part bottom is sent to the upper end of said reverse bed part under said high desorption temperature, therefrom to displace the additional quantity heavy ends under said high desorption temperature;

(e) under said high desorption temperature, discharge heavy ends from the bottom of said reverse bed part;

(f) said level is cooled to low adsorption temp from high desorption temperature;

(g) in said step (b), (c), (d) and (f) during at least one step, the intermediate point of said fluid mixture between said conventional bed part and reverse bed part fed in the said level;

(h) use the said fluid mixture of additional quantity to repeat said step (a)～(g) periodically; Be difficult for selecting the light component of absorption and easily select the reorganization of absorption all under high-recovery, to be reclaimed thereby make with high-purity.

16. the method for claim 15 is wherein feeding said fluid mixture in the said level from said intermediate point during said (a) step.

17. the method for claim 15, wherein during said (d) step with this fluid mixture among said intermediate point is sent into this level.

18. the method for claim 15, wherein every grade includes single adsorbent bed.

19. the method for claim 15, wherein every grade includes the adsorbent bed that separates that is used for conventional bed part and is used for reverse bed part.

20. the method for claim 15, wherein said system comprises two alternating temperature adsorption stage.

21. the method for claim 15, wherein a part of discharging in (b) step is difficult for selecting the light component of absorption to reclaim from this system, another part is used for therein feeding during (d) step one or multistage upper end, and the heavy ends of easily selecting to adsorb in the part that (e) step is discharged are from this system recoveries, and another part is used at it being admitted to during (a) step one or multistage bottom.

22. the method for claim 15, wherein said system comprises two or a plurality of alternating temperature adsorption stage, and heating steps (c) and cooling step (f) comprise fluid is fed another grade that is initially located under the low temperature and makes therebetween pressure balance from being initially located in one-level under the high temperature.

23. the method for claim 15, wherein said fluid mixture comprise as the water of light component that be difficult for to select absorption with as the impurity of easily selecting the heavy ends of absorption.

24. the method for claim 15, wherein said fluid mixture comprise as the argon of light component that be difficult for to select absorption with as the impurity of easily selecting the heavy ends of absorption.

25. the method for claim 15, wherein said fluid mixture comprise as the nitrogen of light component that be difficult for to select absorption with as the carbonoxide impurity of easily selecting the heavy ends of absorption.

26. the method for claim 15, wherein said fluid mixture comprise water and the difficult ethanol of selecting the light component of absorption of conduct that the heavy ends of absorption are easily selected in conduct.

27. the method for claim 15, wherein said fluid mixture comprise as the positive structure hydro carbons of light component that be difficult for to select absorption with as the isomery hydro carbons of easily selecting the heavy ends of absorption.